One vertex per element, one color per generator, with an edge from x to x·s.
(1,2)(3,6)(4,5)(7,8)(9,10,13,16)(11,14,17,20)(12,15,19,22)(18,21,23,24)(25,26)(27,34)(28,32)(29,39)(30,33)(31,36)(35,38)(37,40)(9,11)(10,14)(12,18)(13,17)(15,21)(16,20)(19,23)(22,24)(25,27,28,38,30,37,29,36)(26,31,39,40,33,35,32,34)(2,5)(6,8)(11,17)(14,20)(18,23)(21,24)(25,26)(27,31)(28,39)(29,32)(30,33)(34,36)(35,37)(38,40) involution — undirected(1,3,4,7)(2,6,5,8)(9,12)(10,15)(11,18)(13,19)(14,21)(16,22)(17,23)(20,24)(25,26)(27,35)(28,39)(29,32)(30,33)(31,37)(34,38)(36,40)(12,19)(15,22)(18,23)(21,24)(25,28,30,29)(26,32,33,39)(27,36,37,38)(31,40,35,34)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.